Method and apparatus for controlling and limiting the quantity of &#34;blowthru&#34; steam in a drying system



July 18, 1961 H p, s w c 2,992,493

METHOD AND APPARATUS FOR CONTROLLING AND LIMITING THE QUANTITY OF "BLOW-THRU" STEAM IN A DRYING SYSTEM Filed April 16, 1958 3 Sheets-Sheet 1 SECTION D H11. 25d.

SECTION C SECTION 8 25b SECTION A CONDENSER SEPAR ATINO RECEI R HORACE P. FISHWICK INVENTOR.

y 8, 1961 H. P. FISHWICK 2,992,493

METHOD AND APPARATUS FOR CONTROLLING AND LIMITING THE QUANTITY OF BLOW-THRU" STEAM IN A DRYING SYSTEM Filed April 16, 1958 5 Sheets-Sheet 2 HORACE P. FISHWICK IN VENTOR.

AWN/

y 18, 1961 H. P. FISHWICK 2,992,493

METHOD AND APPARATUS CONTROL G AND LIMITING THE QUANTITY OF "BLOW-T U" STEAM A DRYING SYSTEM Filed April 16, 1958 5 Sheeos--Shee1;v 3

TO 69 AUTOMATlC VALVE 4lc FlG.3

HORACE P. FISHWICK INVENTOR.

BY @MJMM United States Patent 2,992,493 METHOD AND APPARATUS FOR CONTROLLING AND LIMITING THE QUANTITY OF BLOW- THRU STEAM IN A DRYING SYSTEM Horace P. Fishwick, Hanover Center, Mass., assignor to Worthington Corporation, Harrison, N.J., a corporation of Delaware Filed Apr. 16, 1958, Ser. No. 728,833 11 Claims. (CI. 34-48) This invention relates generally to drying systems which include a plurality of rolls receiving steam as a medium to dry the materials brought into contact with the rolls and, more particularly, to a system for automatically controlling and limiting the quantity of blowthru steam in such roll type system. In connection with the manufacture of certain materials such as paper, the material is formed into relatively wet sheets or webs of varying thickness which sheets are passed over a plurality of drying rolls or cylinders to prepare them for final processing.

One known method of heating these rolls is the so called blow-thru principle wherein a quantity of steam is purged through the drying rolls and its siphon means thereby entraining and removing condensate and noncondensable gases as it passes through the rolls. This method of operation insures etficient heat transfer, fast warm-up, and uniform drying of the sheet product in contact with the drying rolls.

Heretofore, depending on the speed of the drying rolls it was customary to maintain a diflerential pressure between the steam inlet and condensate outlet, to overcome both the difference in elevation between the siphon inlet and outlet and centrifugal force, by utilizing an automatic control comprising a diiferential controller and its associated automatic valves, as is illustrated in my article, Design Considerations Affecting Paper Machine Drier Drainage Systems published in Tappi Magazine, vol. 40, No. 6, dated June 1957.

This method, however, presents a problem because there are two steam load conditons. The first, condensing load, is the load produced by radiation losses to the roll itself and the heat used in drying the material passing over the rolls. The second radiation loa occurs whenever the material to be dried is not passing over the rolls. Under the latter condition the quantity of blowthru steam for a given pressure condition is almost double that which occurs under condensing load and thus when the drier is under radiation load, it is necessary to relieve or waste the excess steam or else the operation of the entire machine will be impaired. This Wasted steam is of course an important factor in determining efliciency and cost of operation of the machine,

The present invention overcomes this problem by providing a flow control on the downstream side of the drying rolls which operates to automatically maintain the steam flow through each of the rolls or cylinders in a section at a predetermined minimum quantity regardless of the varying load conditions on the rolls.

There are numerous advantages to be gained from using this improved drying and drainage system, as follows:

(1) A larger percentage of the total paper driers can be operated at high pressure because it is possible to eliminate the usual intermediate section of the typical cascading system. This gives a higher ratio of main driers to wet end condensing drierswhich should result in a somewhat higher evaporation rate.

(2) The wet end group of driers can be sized with greater accuracy than in the past to condense all the blow-thru steam from the remainder of the machine under all load conditions. This flow of blow-thru steam will remain constant whether or not there is a sheet on the machine. The advantage of this is that the vacuum condenser required for a given machine can be of smaller size because it will no longer have to handle sudden surges of steam caused by paper breaks.

(3) Steam saving would result due to the smaller quantity of driers discharging to the condenser and also due to the fact that there will be less steam per drier blowing through.

(4) Floor space would be saved due to the elimination of large separator tanks.

(5) The steam and condensate piping layout would be simpler due to the elimination of some large diameter flash lines.

(6) Lower operating pressures are possible in the main section of driers over that obtainable in the standard cascading single section paper machine because large differential pressures are not carried between the various cascading sections.

Accordingly, it is an object of the present invention to provide a control means for a drying system having a plurality of rolls and operating on the blow-thru principle of steam feeding which will reduce and minimize the quantity of blow-thru steam not only under condensing load conditions but more particularly during radiation load conditions to improve the efiiciency and cost of operation of the system.

It is a still further object of the present invention to provide a drying and drainage system for apparatus of the roll-type wherein a minimum amount of steam will be passed to the condenser and a maximum drying rate will be obtained for the machine.

Further objects and advantages of the invention will become evident from the following description with reference to the accompanying drawings in which:

FIGURE 1 illustrates diagrammatically a drier and drainage system showing the invention for controlling the quantity of blow-thru steam thereon.

FIGURE 2 is a fragment of one of the rolls showing the steam inlet, the condensate outlet, and the siphon means.

FIGURE 3 is an enlarged view of one of the flow meters, and its associated recording flow receiver controller and automatic associated valve.

FIGURE 4 shows a modified form of the control means using a diiferential pressure transmitter.

FIGURE 5 is an enlarged View of the control means illustrated in FIGURE 4.

Referring to the drawings, the invention is illustrated on a drier and drainage apparatus for paper-making which includes a condensing section A, a plurality of drying sections B and C, and a web or felt drying section D, each having a plurality of substantially identical heat transfer rolls or cylinders designated 10.

Section A is disposed at the wet or entering end on which the felt or web W receives the product P to be dried, and section C is disposed at the dry or leaving end Where the finished product P is discharged from the apparatus.

It will be understood that while only four sections are shown wherein each section has a selected number of rolls that this is only for the purpose of illustrating the present invention, as it is well known in the art that the number of sections, as well as the number of rolls or cylinders per section can be varied in accordance with the load requirements of the particular process in which the system is used.

The present invention allows for a more versatile arrangement of the number of rolls in each section as well as the number of sections than has been possible under the prior art cascading type systems because the difierential pressure between the steam inlets and condensate outlets across the rolls in a section is no longer fixed, but now becomes a function of the steam flow through and load on the particular rolls or cylinders.

The heating and drying medium as in the cascading type apparatus will be steam. This steam can be supplied from any suitable source such as a conventional type boiler, not shown, or as exhaust steam from a turbine arrangement also not shown, each of the sections receiving its steam in substantially the same way.

Thus a steam inlet or make-up line 11a is provided for section A, a steam inlet line 11b for sections B and C, and a steam inlet line 110 for section D. Each of these lines 11a, 11b and 11c having an automatically controlled feed regulating and reducing valve as at 12a, 12b and 120 so that during condensing loads varying quantities of steam at the desired pressure will be delivered to the steam inlet manifolds 13a, 13b and 13c for the respective sections. The inlet manifolds 13a, 13b and 13c will in turn pass the steam to the various inlet conduits 14 for the rolls or cylinders in the sections A, B, C, and D.

The feed regulating and reducing valves 12a, 12b and 12c are actuated in response to signals from pressure recording controllers 15a, 15b and 15c. The pressure re cording controllers signal the valves 11a, 11b and 110 to operate in accordance with pressure signals delivered by pressure sensing means 16a, 16b and 160 connected to the respective inlet manifolds 13a, 13b, and 13c. Pressure recording controls of this type can be of any suitable design and are devices which are easily purchasable on the open market and hence not more fully described in the present specification.

FIGURE 2 illustrates one roll or cylinder 10 and shows that on each roll the inlet conduits 14 enter the rolls or cylinders 10 through their respective trunnion bearings about the condensate outlet conduits 17 for the roll. Suitable means are provided in each roll or cylinder 10 such as a siphon means 18 connected to the steam outlet conduits 17 so that the blow-thru steam can purge the condensate and non-condensable gases that collect in the particular roll or cylinder 10.

The conduits 17 are connected to outlet manifolds 19a, 19b, 19c and 19d for the respective sections A, B, C and D. For each of the outlet manifolds a down-leg is formed by lines 20a, 20b, 20c and 20d and separating tanks 21a, 21b, 21c, and 21d where the mixture of unused steam, non-condensable gases and condensate which passes from the outlet manifolds 19a, 19b, 19c and 19d to its respective drop-legs, is separated in the drop-legs so that the unused steam and non-condensables collect in the upper portion of the separator tank and the condensate collects in the lower portion of the separator tanks.

Condensate will be pumped from the separator tanks 21a, 21b, 21c and 21d to waste or some other process requiring the condensate by condensate pumps 22a, 22b, 22c, and 22d, the suction head being maintained on these pumps by control valves 23a, 23b, 23c, and 23d, which are controlled or signalled by the liquid level controllers 24a, 24b, 24c, and 24d, respectively.

The unused steam .and non-condensible gases collected in separating tanks 21a and 21d follows one path to a suitable final condenser while that in 21b and 210 follows a different path to the same condenser. This done to prevent an undue amount of steam being wasted and acts to increase the efiiciency of the apparatus and reduce its cost of operation as much as possible and'obtain the advantages above set forth. It will be understood, however that variations in the path can be made depending on the most effective operative results for a particular process.

Thus in the illustrative form of the, invention the unused steam and non-condensable gases which collect in 1 condensing section A. The unused steam and non-condensable gases from separating tanks 21a and 21d for sections A and D, however, is passed by lines 25a and 25d and connecting conduit 27 to a common duct 28 leading to a vacuum or other suitable condenser 29 communieating with the final separating receiver 30' by a suitable:

duct 31.

In receiver 30 the residue of non-condensed or waste steam, non-condensable gases and condensate is finally separated; Condensate will be pumped from the receiver 30 to waste or some other process as by means of a condensate pump 32 whose suction head is regulated by control valve 33 and liquid level control 34. The noncondensed or waste steam and non-condensable gases are continuously purged from the system by the vacuum pump 35 connected by line 36 to the upper end of re.- ceiver 30.

The broad system above described is similar to that utilized for a cascading type drying and drainage system. However, in a cascading type system the differential pressure between the respective sections is substantially the same differential pressure maintained across the steam inlet and condensate outlet for the rolls in the preceding section. Thus the steam flow on radiation load is not controlled at any predetermined minimum quantity.

In the present invention the various sections are still maintained at pressures wlhich decrease from section to section, the lowest pressure being maintained in the final condensing section A. However, the steam flow through a particular section is set for that predtermined minimum amount of steam needed for the section at maximum roll speed and maximum section tonnage to maintain correct drier evacuation.

Flow meter control arrangement This is accomplished in the form of the invention shown in FIG. 1 by any suitable type of flow meter as at 40a, 40b, 40c and 40d communicating with the lines 25a, 25b, 25c, and 25d on the outlet or downstream side of the rolls 10 of the respective sections A, B, C, and D. The flow meter passes a signal as hereinafter described to its associated automatic control valve shown at 41a, 41b, 41c and 41d also in line 25a, 25b, 25c, and 25d of. the respective sections A, B, C, and D.

This signal can be sent from the flow-meter directly. to the automatic valves or can be passed to an associated recording flow receiver controller as at 42a, 42b, 42c and 42d for the respective sections A, B, C and D. These receiver controls are adapted not only to receive the signal from the flow meter but have mechanism therein to transmit a signal either in proportion to the signal or some modified form of the signal in accordance with the desired operation for the particular section. Thus the signal delivered by the recorder flow. receiver control 42a, 42b, 42c and 42d to the associated automatic valves 41a, 41b, 41c and 41d may be proportional to thesignal received from the associated flow meter 40c, 40c,

40c and 40d or may be a ratio of this signal as a :Eunc-,

tion of operating pressure, temperature, the. machines roll speed, the steam flow or the condensate flow from or mass flow rate-type meters could also be utilized in place of the differential pressure-actuated type flow meterfor passing the desired signal tothe associatedrecording flow meter controllers and the valvesactuated thereby.

Thus, flow meter 40a is shown connectedto theopposites.

sides of an, orifice means 50 in line 25a asit is. knownthat However,

a pressure differential will occur in line 250 on opposite. sldes of the orifice means 50 proportional to the rate of flow through 'line 25c. It will be understood that while an orifice means is illustrated that a Venturi or Pitot tube or combinations of these mechanism for measuring flow rate could be utilized without departing from the spirit of the present invention; the only limitation on the use of one or the other of a combination of these expedients with the flow meter being dictated by the efficiency and accuracy desired.

The higher pressure on the upstream side of the orifice means 50 is continuously transmitted through the high pressure line 51, condensing chamber 52 and line 53 to a float chamber 54. Similarly, the lower pressure on the downstream side of the orifice means 50 is continuously transmitted through the low pressure line 55, condensing chamber 56 and line 57 to a reservoir chamber 58.

Connected to the lowest sections of the reservoir chamber 58 and float chamber 54 is a U-tube means 59 so that float 60, reservoir chamber 58 and U-tube means 59 when filled with the required amount of mercury will operate as a manometer. The diiference in pressure in the float chamber 54 acting to raise or lower the liquid level of the mercury which in turn actuates the float 60.

The movement of the float 60 is conveyed through a crank and lever arrangement 61 to the recording flow receiver control 42c where the lever actuates two operations. First it actuates the pointer 62 through the arm 63 to move across a rotatable recording disc 64 and second it operates a gimbal and flapper means generally designated 65 which mechanism coacts with the nozzle 66 associated with a pilot 67.

The nozzle 66 receives a portion of the supply pressure air passed by line 68 to the pilot valve 67 and it coacts with the pilot valve to modulate the actuating pressure air which is discharged through line 69 to the diaphragm motor 70 of the associated automatically-actuated control valve 41c.

The recording flow receiver controllers for each of the respective sections will operate the valve associated with it to maintain that pressure diflerence across the orifice 50 which produces the desired quantity of steam flow for the respective section.

The flow meter, receiving controllers, and automatic valves herein illustrated are well known in the art and.

accordingly have not been more fully described other than to show theiroperative relationship with the broad drying and drainage system.

The form of the invention illustrated in FIGURE 1 shows the four sections.

, Of these sections the important sections for obtaining proper drying are the condensing section A and the drying sections B and C, and while only two sections are illustrated in the drying section and one section illustrated in the condensing section, it is believed known to those skilled in the art that the condensingsection could have two or more sections and that the drying sections could have as many sections as is necessary for producing the desired operating conditions inaccordance with the load on the particular apparatus.

' Two sections, however, are illustrated in the drying section and one in the condensing section for the purposes of simplifying the illustration of the present invention. The two sections illustrated in. the drying section are toshow that wheresections have the same condensing rate a single controller can be utilized to set the inlet pressure of the steam passing through the inlet manifolds for all respective sections having the same condensing rate.

Thus the blow-thru steam for the drying sections B and C is controlled at the same pressure and quantity by the single control valve i12bactuated to pass a predetermined maximum quantity at the desired pressure to the inlet manifold 13b. H 1

of steam, however, will be-the maximum steam flow that The actual quantity ofblow-thru steam passing through one or the other of these sections, however, is further controlled by its associated flow meter 40b or 40c; the receiver control 42b or 420 and the automatic valves 41b or 410. Each receiver controller is set to deliver a predetermined maximum quantity of steam to the rolls 10 of its section in accordance with the maximum speed of the rolls in the section, the maximum tonnage handled by the section so that correct drier evacuation is maintained.

The respective pressures at which steam is delivered to the various drying and condensing sections will decrease from section to section until the lowest operating pressure is reached at the last section in the condensing section. Thus, in FIGURE 1, section A will be at the lowest pressure.

The predetermined pressure desired in the condensing section A is maintained by means of its pressure controller 15a operating not only the steam inlet or makeup valve 12a but also a blow-down valve 71 which valves 12a and 71 are operated sequentially to maintain the desired lower or differential pressure between this section and the section preceding, from which it receives unused steam and non-condensible gases as above described.

The steam from the blow-down valve 71 is passed by line 72 and lines 27 to the vacuum condenser 29 where other steam and non-condensibles.

Operation In operation, steam is initially admitted through the steam inlet means 11a, 11b and 11c to the inlet manifolds 13a, 13b, and 13c connected thereto at the maximum setting for valves 12a, 12b and 12c. This steam is passed to the various rolls 10 which are placed in rotation with no load other than the web W thereon. The steam will condense in the rolls at the maximum rate because the rolls are at radiation load as there is no material to be dried thereon. This non-condensed or unused steam, non-condensable gases and condensate formed in the rolls will pass through the siphon means to the steam or condensate outlet and outlet manifolds 19a, 19b, 19c and 19a to the down-leg formed by the lines 20a, 20b, 20c and 20d and separating tanks 21a, 21b, 21c and 21d where the mixture is separated and the condensate removed as above described.

The unused steam and non-condensable gases will flow through lines 25a, 25b, 25c, and 25d, and the quantity of steam will be sensed by the flow meters 40a, 40b, 40c and 40d, the steam following the respective paths of flow as above outlined for eflicient operation.

The pressure at which the steam is delivered to any particular section will be regulated by the respective control valves 12a and 12b. In the present system the pressure of the inlet steam to be delivered to sections B and C will be higher than that of the inlet and make-up steam delivered to section A. This pressure setting for a particular section or sections is empirical for each process on which the drying and drainage system is used and in addition to the pressure setting there must be suflicient steam delivered not only to meetthe demands of the system but also to provide proper drier evacuation.

The main advantage of the present invention, however,

is that a greater number of drying sections can be provided because the difierential pressure between the drying sections and thecondensing sections does not control the operation of the system. I

The flow control assembly is not set in accordance with the pressure. .It functions to call for a predetermined minimum quantity of steam needed at maximum machine speed and maximum machinetonnage to maintain correct drier evacuation. This predetermined minimum quantity will occur through a particular section, even when the section will be on radiation load.

' During the initial heating stage a small quantity of steam is passed tothe rolls 10' in a section at the pressure set for that section and'this quantity will be slowly increased until the rolls of the section reach the equilibrium temperature for the pressure setting and the limiting flow rate forthe section.

When the product isdelivered to the web after the rolls have reached operating temperature in the section the steam flowing through the rolls will act to dry the product by delivering their heat through the rolls through the process of condensation.

\ The rate at which condensing occurs in a particular drumorseries of drums in a particular section will control the quantity of steam delivered by the control valve 12b in the case of the drying section and valves 12a and 71 in the condensing section, and the higher the rate of condensation the higher will bethe quantity of steam deliveredto the particular section in order to maintain the pressure setting for the particular section. The quantity of steam delivered can continue to increase up to the maximum setting for the flow meter assembly which will be that predetermined minimum quantity of steam needed at maximum roll speed and maximum roll tonnage to maintain proper drierv evacuation.

. Ifat any time the product P should break or should not be delivered tothe web W for a particular drying section or sections then the rollson these sections will be under radiation load as above described and the condensing load thereon will increase accordingly because of the excessive heat loss which occurs under this particular type load condition. As the condensate increases there will be a corresponding increase in the quantity of steam delivered but as in the case of condensing load this can only increase to that maximum quantity at which the flow meter assembly is set.

Accordingly, the loss of steam or the amount of steam that is wasted during radiation load is limited at least to the extent of this setting.

Section D representing the drier for the web will be on a separate pressure control and a separate purge or blowthru'steam control as indicated in FIGURE 1 of the drawings. Theflow control instrument is set as in the case of the other sections to control only the minimum quantity of steam necessary for proper drier evacuation under the conditions necessary to dry the web properly for further use in .the other sections of the machine. The condensate and unused steam and non-condensable gases from this section are handled separately as has been above described.

Pr essnre difierential transmitter control means FIGURES 4 and 5 show another form of control for accomplishing the same result as that shown in the form of the invention shown in FIGURES 1, 2 and 3. This form of the invention-differs from that previously described inthatthe mechanism for sensing the flow on the downstream side of the rolls will be a difierential pressure transmitter generally designated 140. This transmitter wilLdeliver its signal to a recording flow receiver controller 141 which will be responsive to an air signal rather than a mechanical signal as previously described. This coaction betweentransmitter and controller is known in the:..art as is illustrated in my abovementioned article published in Tappi Magazine.

. Fonpurposes of illustrating this form of the invention a fragmentary portion of FIGURE 1 similar to the position of sectionC was selected with this form of the invention in place of the form abovedescribed. Similar parts ac cordingly bear the same character. numerals and only the relation of the control to these parts is described.

Thus FIGURE .4, ,showing'a.f ragment of the. drying and drainage system and FIGURE 5 illustratethis type transmitter and how it would be applied tothe system in lieu of aflow meter as above described.

FIGURES 4 and 5 show that the respective high and low pressure sides of the orifice 50 are connected to chambers 153 and 154 on opposite sides of a diaphragm element 155.

The differential pressure across the diaphragm element 155 actuates a balanced beam 156 having a flapper mechanism 157 at the end thereof which coacts with a nozzle element 158 connected to the pilot relay 159.

Pressure air is supplied to the diiferential pressure transmitter-through line 160 and the coaction between the flapper 157 and the nozzle 158 act to modulate this pressure air so that the pressure air signalled by the pilot relay 159 through passage 161 and line 162 to the receiving controller 141 will correspond to variations in the differential pressure across the orifice produced by the variations in the flow. This signal delivered to the controller 141 will actuate the mechanism for delivering the corresponding correcting signal through line 163 to the diaphragm motor of the automatic valve 410 in line 250 so that the proper flow through the line 25c will be made in accordance'withthe desired operation of the drying.

and drainage system as above described.

It is known that the optimum blow-thru rate will exist for each load condition on the machine. Therefore, by means of a ratio controller the quantity of blow-thru steam can be varied as a function of operation pressure, temperature or machine speed. Also as a function of steam flow to the machine or condensate flow from the machine.

As an illustration, it would be a fairly simple matter for those skilled in the art to place aratio flowcontroller at the discharge of the condensate pumps and measure the condensate flow which of course is a measure of the steam condensed in the driers. Then if you wished the blow-thru steam to be twenty percent of the condensed steam at all times the ratio controller instrument could be set so as to throttle the bloW-thru steam control valve to at all times maintain this desired ratio.

This modification of the system will beunderstood clearly by those skilled in the particular art.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a drier and drainage system including a lurality of sections each having a plurality of heat transfer" rolls therein the method of controlling such system which includes the steps of passing blow-thru steam at a predetermined pressure to the rolls in each of said sections, condensing a portion of the steam in said rolls and purging condensate and non-condensable gases from, the rolls in each section, measuring the flow of unused steam and non-condensable gases flowing out of the downstream side of the rolls in each section, regulating the downstream flow of unused steam and non-condensible gases in accordance with the measured value of the steam flow to limit the steam flow to that predetermined minimum quantity needed under all conditions of operation to maintain correct drier evacuation, and purging waste steam and non-condensable gases from the system.

2. In a drier and drainage system including a plurality of sections each having a plurality of heat transfer rolls therein the method of controlling such system which includes the steps of passing blow-thru steam at a predetermined pressure to the rolls in each of said sections, adjusting the steam inlet pressure of each section at a pressure less than the preceding-section, condensing a portionof .the steam in said rolls and purging condensate and.non-.condensable gases from the rolls in each section, measuring the flow of unused steam and non-condensable gases flowing out of the downstream side of the rolls in each section, regulating the downstream flow of unused steam and non-condensible gases in accordance with the measured value of the steam flow to limit the steam flow to that predetermined minimum quantity needed under all conditions of operation to maintain correct drier evacuation, and purging waste steam and non-condensable gases from the system.

3. The method of controlling a drying and drainage system as claimed in 1 wherein regulation of the downstream flow of unused steam and non-condensible gases is proportional to variations in the measured value of the steam flow.

4. In a drier and drainage system including, a plurality of independent drying sections, each of said sections having a plurality of heat exchange rolls, the combination of, an inlet and an outlet for each of said rolls,- steam inlet manifold means connected to the respective, inlets for said roHs and to a source of steam, control valve means in said steam inlet manifold means to regulate the flow and pressure of steam delivered to the rolls for each respective section, outlet manifold means connected to the respective outlets for said rolls to receive unused steam, condensate and non-condensable gases, flow sensing means operatively associated with each of said outlet manifold means to sense the flow of unused steam, valve means in said outlet manifold to regulate the flow of unused steam therethrough, control means for actuating said valve responsive to signals from said flow sensing means and to limit the flow of unused steam through said rolls to a predetermined minimum quantity at radiation load, and condensing means connected downstream of said valve means to remove unused steam and non-condensable gases from the system.

5. In a drier and drainage system including, a plurality of independent drying sections substantially adjacent.

each other, each of said sections having a plurality of heat exchange rolls, the combination of, an inlet for each of said rolls, steam inlet manifold means connected to the respective inlets for said rolls and to a source of steam, control means in said steam manifold means to regulate the flow and pressure of steam delivered to the rolls for each respective section, outlet means for each of said rolls to purge unused steam, condensate and non-condensable gases therefrom, separating means coacting with said outlet means for separating said unused steam, condensate and non-condensable gases, flow sensing means operatively associated with said separating means to sense the flow of unused steam from said separating means, valve means in said outlet means to control the flow of unused steam therethrough, control means for actuating said valve means responsive to signals from the ilow sensing means and to limit the flow of unused steam through said rolls to a predetermined minimum quantity at radiation load, and condensing means connected to said separating means downstream of said valve means to remove unused steam and non-condensable gases from the system.

6. In a drier and drainage system as claimed in claim 5 wherein said sensing means includes an orifice mechanism adapted to signal the differential pressure thereacross.

7. In a drier and drainage system as claimed in claim 5 wherein said control means comprises, a recorder flow receiver controller means connected to the sensing means, said receiver controller adapted to deliver a signal proportional to the signal received from the flow sensing means.

8. A drier and drainage system including a condensing section and a plurality of drying sections, each of said sections having a plurality of heat exchange rolls, the combination therewith of, inlet means for each of said rolls, an inlet manifold for each of said sections connected to a source of steam and to the means for the rolls of its respective section, a control valve coacting with each of said inlet manifolds to regulate the pressure of the steam delivered to the rolls in the respective sections whereby each drying section can be regulated at a delivered steam pressure higher than that of the next successive section, outlet means for each of said rolls to purge unused steam, condensate and non-condensable gases therefrom, an outlet manifold for each of said sections connected to the respective outlet means for the rolls in said section adapted to separate unused steam and condensate, flow sensing means operatively associated wtih each of said outlet manifolds to sense the flow of unused steam therethrough, valve means connected in each of said outlet manifolds downstream of said flow sensing means to regulate the flow of unused steam through said rolls, control means for actuating said valve means responsive to said flow sensing means and to limit the flow of unused steam through said rolls to a predetermined minimum quantity at radiation load, and condens ing means connected in said system downstream of said valve means to remove unused steam and non-condensable gases from the system.

9. In a drier and drainage system including a condensing section and a plurality of drying sections, each of said sections having a plurality of heat exchanger rolls, the combination of, inlet means for each of said rolls, an inlet manifold for each of said sections connected to a source of steam and to the inlet means for the rolls of its respective section, a control valve coacting- With each of said inlet manifolds to regulate the pressure and quantity of steam delivered to the rolls in the respective section whereby said drying sections can be regulated at a delivered steam pressure higher than that of said condensing sections, outlet means for each of said rolls to purge unused steam, condensate and non-oondensable gases therefrom, an outlet manifold for each of said sections connected to the respective outlet means for the rolls in said section, separating means operatively connected to each of said outlet manifolds to separate said unused steam and condensate, a liquid outlet for said separator means, means for prevent-ing unused steam and non-condensable gases from discharging through said liquid outlet, flow sensing means operatively associated with each of said outlet manifolds to sense the flow of unused steam therethrough, valve means connected in each of said outlet manifolds downstream of said flow sensing means to regulate the flow of unused steam through said rolls, control means for actuating said valve means responsive to said flow sensing means and to limit the flow of unused steam through said rolls to a predetermined minimum quantity at radiation load, and condensing means connected in said system downstream of said valve means to remove unused steam and non-condensable gases from the system.

10. In a drier and drainage system including a condensing section and a plurality of drying sections, each of said sections having a plurality of heat exchange rolls, the combination of, inlet means for each of said rolls, an inlet manifold for each of said sections connected to a source of steam and to the inlet means for the rolls of the respective section, a control valve coacting with each of said inlet manifolds to regulate the pressure of the steam delivered to the rolls in the respective sect-ions whereby said drying sections can be regulated at a delivered steam pressure higher than that of the condensing sections, outlet means for each of said rolls to purge unused steam, condensate and non-condensable gases therefrom, an outlet manifold for each of said sections connected to the respective outlet means for the rolls in said sections, a separating means coacting with each of said outlet manifolds to separate unused steam and noncondensable gases from the condensate delivered thereto, separating means conduits for unused steam and noncondensable gases and a liquid outlet for condensate, means for preventing unused steam and non-condensable gases from discharging through said liquid outlet, flow sensing means connected in each of said separating means conduits to sense theflow of unused steam therethrough from'rsaid' separating: means, valve means in each of said separating means conduits downstream of said flow sensing means, control means for actuating said valve means'responsive to signals from said flow sensing means andto'limit the flow of unused steam through said rolls toa predetermined minimum quantity at radiation load, condensing means, said conduit means from the separating means for the condensing section connected to said condensing means downstream of the control means to reniove unused steam andlnon-condensab les from the system. l

11. In a drier and drainage system including a condensing sectionand a plurality of drying sections, each of said sections having a plurality of heat exchange rolls, the combination of, inlet means for each of said rolls, an inlet manifold for each of said' sections connected to a-source of steam and to the inlet means for the rolls of the respective section, a control valve coasting with each of saidinlet manifolds to regulate the pressure of the steam delivered to the rolls in the respective sections whereby said drying sections can be regulated at a delivered steam pressure higher than that of the condensing sections, outlet means for each of said rolls to purge unused steam, condensate and non-condensablegases therefrom, an outlet manifold for each of said sections connected to the respective outlet means for the rolls in saidiseetion, separating means coacting with said outlet manifold to'receive and separate unused steam condensate and non-condensable gases received therefrom, a conduit means for each of said separating means to pass unused'steam and non-condensable gases therefrom, the conduitmean's for the separating means for the drying section connected to the inlet manifold of the condensing section, sensing means in saidconduit means forthe drying section to sense the quantity of unused steam flowingtherethrough, valve means in said conduit means for the drying section downstream of said now sensing means, control means for actuating said valve means re sponsive' to signals from said flow sensing means and to limitthe flow of unused steam through said drying sec tion rollsto'a predetermined minimum quantity at radiation load, conduit means for the separating means for the condensing section, vacuum means connected to said conduit means for the condensing section to purge unused steam and non-condensab'le gases from the drier and drainage system, a second sensing means in said second mentioned conduit means, and a second valve means in 'said conduit means for the condensing section downstream of said secondflow sensing means, a second control means for actuating said second valve means responsive to said second sensing means to limit the flow of un used steam through said condensing section to a predetermined minimum quantity at radiation load.

References Cited in the file of this patent UNITED sTATEs PATENTS OTHER REFERENCES Paper Machine Drying and Drainage Systems, Bulletin No. RD. 113, Masoneilan Division of Worthington Corp., June 1957. (Copy available in Div. 49.) 

